Moderate -0.3 This is a straightforward application of the power rule for differentiation followed by solving a quadratic inequality. While it requires two steps (differentiate, then solve f'(x) > 0), both are standard C2 techniques with no conceptual challenges, making it slightly easier than average.
Question 4:
4 | 6x2 + 18x 24
their 6x2 + 18x 24 = 0 or > 0 or 0
−4 and + 1 identified oe
x < 4 and x > 1 cao | B1
M1
A1
A1
[4] | or x ≤ 4 and x ≥ 1 | or sketch of y = 6x2 + 18x 24 with
attempt to find x-intercepts
if B0M0 then SC2 for fully correct
answer
Differentiate $2x^3 + 9x^2 - 24x$. Hence find the set of values of $x$ for which the function $f(x) = 2x^3 + 9x^2 - 24x$ is increasing. [4]
\hfill \mbox{\textit{OCR MEI C2 Q4 [4]}}